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THE AMERICAN NATURALIST [Vol.LVI 



duced characteristic pulmonary lesions when injected into 

 other cats. Similarly autolysed lung-tissue of other 

 mammals had no effect on cats. 



But, the question arises, in order to get parallel influ- 

 ences, in soma and germ, would there not have to be ab- 

 solute identity between the two sets of proteins con- 

 cerned? Before answering this question let us glance 

 for a minute at two types of specificity which are recog- 

 nized in serological reactions : namely, ' ' species-specific- 

 ity " and " organ-specificity." What the serologist 

 means by species-specificity is the fact, shown through 

 precipitin reactions, that blood immunized against one 

 tissue of an alien species will react, although in a less 

 degree, with extracts of the other tissues of that species. 

 And that there may be a specificity of certain organ com- 

 plexes which is independent of species is shown by the 

 fact that an immune serum produced by using the crys- 

 talline lens of one species of animal yields a precipitin 

 which reacts more or less with the lens proteins of even 

 unrelated species. Similar results have been obtained 

 with proteins derived from the testis, and confirmatory 

 evidence of such organ-specificity has also been estab- 

 lished by means of anaphylactic reactions. Such facts 

 as these, together with those cited in the discussion of the 

 gradational reactions of various immune sera according 

 to the systematic relationships of animals, it seems to me, 

 answer our question affirmatively; there need not be ab- 

 solute identity between the proteins of the somatic cells 

 and their correlatives in the germ-cells for immune sera 

 engendered against the one to react also against the 

 other. I raise the issue because it might be urged that 

 such tissues of an organism as become so abnormal as to 

 excite the production of antibodies are no longer sufii- 

 ciently similar to the normal tissue-elements, and there- 

 fore to their germinal representatives, to make the anti- 

 bodies effective against either normal somatic or ger- 

 minal constituents. 



It seems to me that all available facts indicate that the 

 constitution of an ()rganis;iii, whether germ or soma, is 

 not to ])e v('.ii.;n<lc(l a cDtigeries of cooperating, equi- 

 potent unit-, l)iit rather as the outcome of interacting 

 systems which differ in their orders of organization; sys- 

 tems which in themselves possess more fundamental and 



